The system has a firmware password set, so unless you know the password multiple failed attempts with send you down this path.
Apple went to great lengths to protect the system from snooping with the T1 chip and even went further with the T2 chip and forward with the newer M series system.
If you are the original owner you could see if Apple will unlock the system using your iCloud account. But you will need to physically visit an Apple Store with hard proof you are you!
The tricks we had used in older systems no longer work in T1 or newer systems. So no, you can’t cheat your way out booting up on an external drive, thinking you can then install a new OS to over come the firmware password.
crwdns2934105:0crwdne2934105:0
crwdns2934113:0crwdne2934113:0
crwdns2915270:0crwdne2915270:0
crwdns2889612:0crwdne2889612:0
0